1. Field of the Invention
The present invention relates to a substrate processing method, a substrate processing apparatus and a substrate carrying method.
2. Description of the Related Art
In a photolithography process in fabrication processes for the semiconductor device, for example, resist coating treatment for forming a resist film on a wafer surface, exposure processing in which a pattern is irradiated on the wafer and exposed, post-exposure baking treatment for heating the wafer after the exposure processing, developing treatment for performing development for the heat-treated wafer and the like are performed in sequence. These processing and treatments are sequentially performed in processing and treatment units separately provided in a single coating and developing treatment system and an aligner adjacent to the system. The coating and developing treatment system is structured to process a plurality of wafers concurrently at the same time, in which normally one carrier carries the wafers between the above-mentioned processing and treatment units.
The carrier is configured to freely access the plurality of processing and treatment units and its operation is controlled to carry the wafers in the processing and treatment units at preferable timing in accordance with the processing steps to the processing and treatment units in which the respective following steps are performed, so that a series of the photolithography processing steps is smoothly performed.
However, one carrier carries a number of wafers as described above, and thus in the case where, for example, when the carrier is carrying one wafer in one processing or treatment unit, treatment for another wafer is completed in another processing or treatment unit, the carrier can not carry the other wafer before it finishes carrying the one wafer. Meanwhile, when the carrier is not carrying a wafer but in a waiting state, the carrier can immediately carry the other wafer. Accordingly, the period required after the treatment for a wafer finishes and before the carrier goes to receive the wafer depends on the position and the state of the carrier, presenting a fear that the total periods required from the end of one treatment to the start of the following treatment become nonuniform between the wafers.
When a so-called chemically amplified resist is used as a resist solution for forming the aforementioned resist film, exposure generates acid, and the resist film reacts with the acid and the resist film in the exposed portion changes to be soluble in the developing solution. Therefore, the degree of the developing treatment, that is, the line width of the circuit pattern on the wafer, greatly depends on progress of the chemical reaction by the acid, and the chemical reaction is greatly affected by the period from the exposure to the development.
Accordingly, the period after the wafer is subjected to the exposure processing and before the developing treatment, especially, the period required from the exposure processing to the post-exposure baking treatment is affected by the position and the state of the carrier to be nonuniform, presenting a fear of adversely affecting the line of the circuit pattern which is finally formed on the wafer.
Further, the aforementioned carrying of the wafer is conducted as follows, normally a main controller for controlling the carrier receives a processing end signal from each processing or treatment unit and stores it, the carrier recognizes the stored processing end signal every completion of the carrying of one wafer, and the carrier verifies it and then moves to the processing or treatment unit that is the sender to carry the wafer for which predetermined processing has been completed in the processing or treatment unit to the processing or treatment unit where the following step is performed.
According to the above-described control mechanism for the carrier, however, since the carrier finishes the carrying of the present wafer and verifies processing end signal in the main controller, and then moves to the processing or treatment unit that is the sender, the period after the processing or treatment for the wafer finishes in the processing or treatment unit and before the carrier goes to the processing or treatment unit to receive the wafer differs depending on the state of the carrier at the moment or the number of the processing end signals, and generally tends to be longer. Therefore, it is impossible to carry the wafer between the processing and treatment units speedily and in a fixed period.
Especially when the chemically amplified resist solution is used as described above, a treatment is performed in which the acid, as a catalyst, generated in the resist film by the exposure is increased in temperature to activate, promoting the chemical reaction for making the resist film soluble in the developing solution in the post-exposure baking treatment. In the following cooling treatment, a treatment of decreasing the acid in temperature to stop the catalysis of the acid is performed. Therefore, unless the wafer is speedily carried between the post-exposure baking unit and the cooling treatment unit, the wafer is overbaked to cause the chemical reaction to excessively proceed by the catalysis of the acid to widen the width of the resist film soluble in the developing solution, resulting in too wide line width of the circuit pattern which is finally formed on the wafer. Furthermore, if the wafer is not carried between the post-exposure baking unit and the cooling treatment unit in a fixed manner, there is a fear that line widths of the circuit patterns formed on wafers will become nonuniform between the wafers.